1. Field of the Invention
The present invention relates to processes for producing guanosine 5′-diphospho-fucose (hereinafter referred to as “GDP-fucose”) and guanosine 5′-diphospho-4-keto-6-deoxymannose (hereinafter referred to as “GKDM”) GDP-fucose is useful, for example, as a synthetic substrate of complex carbohydrates which are useful, for example, for application to and immunotherapy for the protection against infections by bacteria, viruses and the like and cardiovascular diseases. Also, GKDM is useful as, for example, an intermediate for the production of GDP-fucose.
2. Brief Description of the Background Art
As a process for producing GDP-fucose, a chemical synthesis process (Carbohyd. Res., 242: 69 (1993)) is known; however, it has disadvantages in terms of stereoselectivity and the supply of a substrate. The processes in which enzymes are used (Agric. Biol. Chem., 48: 823 (1984), WO 93/08205, and WO 99/09180) are not suitable for large scale production since they use expensive materials. Also, the enzymes require complex purification steps. A process using the activity of a microorganism has been developed (WO 98/12343) and is a useful process; however, it requires further modification for use as an industrial production process. In addition, it is known that the activity of GDP-mannose 4,6-dehydratase as the starting enzyme in the biosynthesis of GDP-fucose from GDP-mannose is inhibited by the final product, GDP-fucose (Biochim. Biophys. Acta, 117: 79 (1966); FEBS Lett., 412: 126 (1997)).